The present invention relates to a double clutch for a transmission having two input shafts which are coaxially arranged. Since a transmission having one input shaft is used in the related art, one clutch disc is also used to transmit power from an engine to the transmission or block the same. However, a double clutch transmission having two shafts is required to use a double clutch having two clutch discs so as to transmit power from the engine. Such a double clutch needs two clutches, is configured of a dual operation gear type, and allows a double shaft to be changed whenever the double clutch is shifted one at a time, thereby enabling shift speed to be high and helping in improving actual fuel efficiency.
In particular, a dry double clutch transmits power of an engine to a transmission by friction between a clutch disc and a pressure plate without use of oil, unlike a conventional wet double clutch. Such a dry double clutch, particularly a dry double clutch designated by reference numeral 101 in FIG. 1, transmits power of an engine to a transmission by friction between a clutch disc and a pressure plate without use of oil, unlike a conventional wet double clutch. Such a dry double clutch designated by reference numeral 101 in FIG. 1 is divided into a set double clutch 102 and a damper flywheel 103.
Among of them, the set double clutch 102 has a central plate 105 coupled to a connection plate 107 by connection rivets 108, and the central plate 105 enables a first pressure plate 109 and a second pressure plate 111 to rotate by pressing first and second clutch discs 113 and 115. The first clutch disc 113 is located to an engine side of the central plate 105 through a first hub 117, and the first hub 117 is coupled to a transmission inner input shaft 119. The second clutch disc 115 is located to a transmission side of the central plate 105 through a second hub 121, and the second hub 121 is coupled to a transmission outer input shaft.
In this case, the first clutch disc 113 is configured such that a first drive plate 123 is coupled to the first hub 117 by an assembly structure consisting of a stopper ring 125, a retainer ring 127, and a snap ring 129, as shown in FIG. 2. As shown in FIG. 1, the stopper ring 125 and the retainer ring 127 are respectively pressed against inner and outer sides of the first drive plate 123 by rivets 131 passing through the first drive plate 123 so as to prevent the first hub 117 from being decoupled from the first drive plate 123.
In addition, the damper flywheel 103 includes a primary wheel 110 which is coupled to a crankshaft of an engine by bolts, a primary cover 130 which covers an upper portion of the primary wheel 110, a drive plate 120 which transmits power of the engine inside the primary wheel 110 and the primary cover 130, and the like. In addition, the power of the engine is transmitted from the damper flywheel 103 to the set double clutch 102 by a spline type connector 130, and a spline gear is formed on an outer peripheral surface of the connector 130. In addition, the set double clutch 102, to which the power is transmitted by engaging with the spline gear, is configured such that the connection plate 107 spline-coupled with the connector 130 is coupled to the set double clutch 102. In this case, the connection plate 107 has a circular shape formed at a center thereof with a hole, and includes an extension portion is radially coupled to the set double clutch 102. The hole has a hub structure, and forms a spline gear corresponding to the connector 130. Accordingly, the damper flywheel 103 and the set double clutch 102 transmit the power by means of spline coupling between the connector 130 and the connection plate 107.
However, in a case of spline coupling, backlash may be generated due to tolerance between teeth of a gear and teeth of another gear, and thus impact is applied to the teeth of the gears during rotation of the gears in a clockwise or counterclockwise direction. Particularly, in power transmission of a vehicle, the damper flywheel and the set double clutch rotate relative to each other in the clockwise or counterclockwise direction during acceleration and deceleration of the vehicle. In this case, the backlash causes impact and noise in the connector and the connection plate, deterioration of damping performance in the rotation direction, and reduction in durability of the vehicle. Furthermore, since the impact and noise are transferred to a driver during driving of the vehicle, there is a problem in that it may also be uncomfortable to ride in.
In addition, since the stopper ring 125 supporting the first hub 117 comes into direct contact with the first hub 117, axial vibration generated in the first hub 117 during shifting is transferred as it is to the stopper ring 125. Therefore, there is a problem in that durability of the stopper ring 125 is deteriorated.
Moreover, the first hub 117, which is assembled to or disassembled from the first drive plate 123 during assembly or disassembly of the dry double clutch 101, may apply impact to the stopper ring 125. Therefore, there are problems in that, due to the impact when such assembly or disassembly is repeated, the stopper ring 125 is damaged to deteriorate durability thereof and assembly work is difficult.